The European Convention on Human Rights is rapidly evolving into a cosmopolitan legal order: a transnational legal system in which all public officials bear the obligation to fulfill the fundamental rights of every person within their jurisdiction. The emergence of the system depended on certain deep, structural transformations of law and politics in Europe, including the consolidation of a zone of peace and economic interdependence, of constitutional pluralism at the national level, and of rights cosmopolitanism at the transnational level. Framed by Kantian ideas, the paper develops a theoretical account of a cosmopolitan legal system, provides an overview of how the ECHR system operates, and establishes criteria for its normative assessment.